Is Lack of Sleep Causing Your Brain to Shrivel?

Snore a lot? Get up frequently at night to urinate? Wake up at 2 A.M. with bright ideas or worries? All these disruptions of sleep are common and more so as we get older. Does it matter? Well, of course such awakenings disrupt our sleep, and maybe it is just inconvenient. But disrupted sleep not only is more likely with age, it may promote deterioration in mental functioning. A recent study compared the effects of sleeping behavior in young adults and seniors. The study involved assessing the memory after sleeping of 18 young adults in their 20s and 15 older adults in their 70s. The subjects were tested on 120 word sets before they went to bed, and an EEG machine monitored their brain activity while they slept. Upon awakening, they were tested once again on the word pairs, but this time they took the tests while undergoing functional magnetic resonance imaging (fMRI) scans.

The quality of deep sleep among the older adults was 75 percent lower than the younger ones, and their memory was significantly worse the next day−55 percent worse. The scans suggested deterioration of the frontal lobe. Shrunken brains can occur from aging and shrunken brains impair thinking and memory. But is it possible we have the cause and the effect backwards. Maybe what happens in the environment, such as impaired sleeping, causes both the shrunken brain and the impaired memory. Or in other words, what causes older brains to shrink?

Scientists consider a decrease of about 2% shrinkage every 10 years as normal. That may not be normal, just what most people experience because they are not taking care of their brains. There is abundant research that shows that exercises for both the brain and body help to reduce brain atrophy.

Of course, anything that damages neurons can reduce the number of their tree-like processes and the density of their contact points with other neurons. The list of such causes is long, including: alcohol abuse, brain inflammation, certain infections, concussion, impaired blood supply, lack of intellectual stimulus, vitamin B12 deficiency. It now appears that we should add fragmented sleep to the list.

Common natural causes of fragmented sleep in older humans are alcohol abuse and sleep apnea. Also, in males, enlarged prostate causes a need for frequent urination. As I have explained in my learning and memory blog posts (thankyoubrain.blogspot.com), learning events during the day are consolidated into lasting form during the sleep at night of the same day. We don’t know exactly how sleep helps, but obviously, you have far fewer mental distractions during sleep — unless, of course you keep waking up.

Alzheimer’s Disease also causes fragmented sleep. So, it is no surprise that the brain degeneration by the disease would cause memory problems. But maybe, just maybe, it is the fragmented sleep that accelerates onset of Alzheimer’s disease. Now, this seemingly ridiculous possibility has to be taken seriously in light of new research showing that sleep-disordered breathing, as in sleep apnea, seems to increase the risk of mental decline and even dementia in older women.

Disrupted sleep may also accelerate normal aging. This is certainly true when the cause is sleep apnea, which raises blood pressure and increases the cardiovascular damage that high blood pressure causes. Blood clotting is promoted, increasing the likelihood of strokes. Obesity and diabetes are often associated with sleep apnea, and it seems that sleep apnea not only results from obesity but can promote obesity and the diabetes that often accompanies obesity. Diabetes is toxic for nerve terminals. Similar neuropathy may also be occurring in their brain. Sleep apnea causes daytime sleepiness, and that it turn reduces attentiveness and mental activity, which when sustained over many years reduces the mental stimulus and promotes atrophy of neuronal processes.

Obviously, blood oxygen drops during sleep apnea. Normally, blood is 94% to 98% saturated with oxygen. But not breathing for 30 seconds or more during sleep causes oxygen level to drop to 80% or less. Any level below 90% oxygen level is dangerous, especially to the brain which demands nearly 20% of all the body’s oxygen supply. The adult brain can only survive about four minutes once oxygen is completely cut off.

So it is entirely possible that the slipping memory we see in so many elderly is a warning sign of something much more serious. But by the time the memory deficits show up, much of the damage has already been done. Prevention is the best hope.

Fragmented sleep could very well cause a steady loss in memory and even lead to some people developing Alzheimer's disease and other types of dementia. This lowering of the amount of deep sleep a person goes through can cause many problems in a person's memory, given that if a person is unable to go through deep sleep, it is much less likely that they will remember it later on. Extreme cases of sleep apnea could also very well cause shrinkage in the brain, considering that the brain needs a certain amount of oxygen in the blood, otherwise the brain begins to shutdown, and a prolonged exposure to this sort of problem would cause many issues in the brain. Although, the study stated at the beginning of the article has rather low external validity, given that only 33 subjects were tested. What also must be taken into account in this study is that those who were in their 20s are much more likely to still be in school and, then, much more used to these types of memory activities, giving them an unfair advantage on those who are older and have possibly not been actively training their brains in the way that those in their 20s have.

1. One post that is stupid does not automatically make the whole blog site stupid.

2. The critic complains about drawing causal inferences from the observation that three things correlated: fragmented sleep, poor memory capability, and shrunken brains. But this study was a published peer-reviewed paper. Let's chastise the journal not the reporter of this post. Moreover, the experiments met conventional standards: there was an experimental control group in which the correlations mentioned above did not occur.

3. The critic's criticism is that correlation does not confirm causation. True, but it does imply it, especially when there is other supporting information and logic. The only way to satisfy the more stringent requirement is to conduct longitudinal studies in the same person, monitoring sleep patterns, memory performance, and brain volume periodically over their lifetime. Are you ready to fund that research? Why don't we just stop research altogether because to do it "right" would cost way too much in time and money.